Creating a hollow cylinder geometry

[Tbuttts21]

I've been reading through the FDS manual and am trying to determine a good way (if one exists) to create a hollow cylinder geometry. I know that you can create cylinders using &GEOM, but I want it to be hollow instead of solid.

Is there a good way of doing this? Or should I just attempt to create it manually?

[marcosvanella]

You can make it using preprocessors, either BlenderFDS or Pyrosim.

[Tbuttts21]

Yes, that is true. I was hoping there was a way to do it in FDS itself so I could automate a process in Python.

[marcosvanella]

Then I'd say you need to build the triangulation in python using your hollow cylinder parameters. We don't have a hollow cylinder feature currently. Another option (haven't tried it) would be using an extruded polygon with the cross section shape of the tube as a closed "C", but that might be just as costly on your side.

[emanuelegissi]

BlenderFDS is written in Python ;-) Il ven 15 dic 2023, 18:44 marcosvanella ***@***.***> ha scritto:

…

Then I'd say you need to build the triangulation in python using your hollow cylinder parameters. We don't have a hollow cylinder feature currently. Another option (haven't tried it) would be using an extruded polygon with the cross section shape of the tube as a closed "C", but that might be just as costly on your side. — Reply to this email directly, view it on GitHub <#12286 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACXMVY7X2ZXL445MU7W26QDYJSEANAVCNFSM6AAAAABAWXWQROVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM3TQNRWGYYTK> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Koranten]

Can I write an .STL file with a CAD software other than BlenderFDS, and read this STL file with FDS? I'm trying to do this hollow cylinder stuff.

[rmcdermo]

If you are going to be using FDS with complex geometry, I highly recommend you either learn BlenderFDS or Pyrosim. As someone who had to learn Blender and BlenderFDS, I admit it is a heavy lift. But there are numerous youtube videos for helping you. And, as Emanuele points out, it is scriptable, though I have not yet even gotten that far. I have found that the new MOVE feature in FDS means I can just make geometries in a simple way in Blender and then export to the FDS format and MOVE (also does reorientation) however I need to. Creating a hollow cylinder in BlenderFDS is not hard once you know have a basic handle on Blender. Again, not saying this is trivial, only that you are better off investing your time learning this than in writing a one off script for generating the FDS geometry. No, you cannot just import the STL into FDS. You'd first have to get it into Blender anyway, so I find it much easier usually to just build the geometry in Blender. My two cents...

[Koranten]

Ok, thanks. I'm not going to do complex geometries, it's really just gonna be a cylinder room. I already used BlenderFDS in the past to create the blocks of a cylinder room, but it was blocky by definition years ago. Now I'd like to use the new beta GEOM stuff to have a smooth hollow cylinder, so I guess I'm going to BlenderFDS again.

[aleclementi]

Hi @Tbuttts21 ,

I had the same issue while trying creating a hollow horizontal cylindrical vessel. Eventually I used a script in blender fds.
vessel5m.zip

GEOM makes it smoother, however has limitations. In my case for example i needed to spray water over the cylinder, but the way FDS treats the drops at equatorial line (they fall straight down) did not serve my case. So I had to use the "blocky" approach.